docs: def _as_mpl_axes(self):
          """
          Another moderately mind-bendy method. When ``matplotlib`` is provided a projection via a ``projection`` keyword
          argument, it expects to get something with a callable ``as_mpl_axes`` method. The precise details of what this
          method does, exactly, are not important: it suffices to know that every ``cartopy`` coordinate reference system
          object has one.
  
          When we pass a ``geoplot.crs`` crs object to a ``geoplot`` function, the loading and centering of the data
          occurs automatically (using the function defined immediately above). Since we control what ``geoplot`` does at
          execution, we gracefully integrate this two-step procedure into the function body.
  
          But there are also use cases outside of our control in which we are forced to pass a ``geoplot.crs`` object
          without having first called ``load``: most prominently, when creating a plot containing subplots, the "overall"
          projection must be pre-loaded. It's possible to get around this by using ``cartopy.crs`` objects instead,
          but this is inelegant. This method is a better way: when a ``cartopy.crs`` object called by ``matplotlib``,
          it silently swaps itself out for a vanilla version of its ``cartopy.crs`` mirror, and calls that function's
          ``_as_mpl_axes`` instead.
  
          Parameters
          ----------
          proj : geoplot.crs projection instance
              The instance in question (self, in the method body).
  
          Returns
          -------
          Mutates into a ``cartopy.crs`` object and returns the result of executing ``_as_mpl_axes`` on that object instead.
  
          """
          proj = self.load(gpd.GeoDataFrame(), dict())
          return proj._as_mpl_axes()